Publications by authors named "Peter Nickerson"

122 Publications

Change in Estimated GFR and Risk of Allograft Failure in Patients Diagnosed With Late Active Antibody-mediated Rejection Following Kidney Transplantation.

Transplantation 2021 Mar;105(3):648-659

Department of Medicine, University of Wisconsin, Madison, WI.

Background: There are challenges in designing adequate, well-controlled studies of patients with active antibody-mediated rejection (AMR) after kidney transplantation (KTx).

Methods: We assessed the functional relationship between change in estimated glomerular filtration rate (eGFR) following the diagnosis of AMR and the risk of subsequent death-censored graft failure using the joint modeling framework. We included recipients of solitary KTx between 1995 and 2013 at 4 transplant centers diagnosed with biopsy-proven active AMR at least 1 year post-KTx, who had a minimum of 3-year follow-up.

Results: A total of 91 patients across participating centers were included in the analysis. Of the 91 patients, n = 54 patients (59%) met the death-censored graft failure endpoint and n = 62 patients (68%) met the all-cause graft failure composite endpoint. Kaplan-Meier death-censored graft survival rates at 12, 36, and 60 months postdiagnosis of AMR pooled across centers were 88.9%, 58.9%, and 36.4%, respectively. Spaghetti plots indicated a linear trend in the change in eGFR, especially in the first 12 months postdiagnosis of active AMR. A significant change in eGFR was observed within the first 12 months postdiagnosis of active AMR, getting worse by a factor of -0.757 mL/min/1.73 m2 per month during the 12-month analysis period (a delta of -9.084 mL/min/1.73 m2 at 1 y). Notably, an extrapolated 30% improvement in the slope of eGFR in the first 12 months was associated with a 10% improvement in death-censored graft failure at 5 years.

Conclusions: If prospectively validated, this study may inform the design of pivotal clinical trials for therapies for late AMR.
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http://dx.doi.org/10.1097/TP.0000000000003274DOI Listing
March 2021

Age and sex determine conversion from immediate-release to extended-release tacrolimus in a multi-center cohort of Canadian pediatric renal transplant recipients.

Pediatr Transplant 2020 Dec 23:e13959. Epub 2020 Dec 23.

Pediatric Nephrology, The University of British Columbia, Vancouver, BC, Canada.

ER-Tac, taken once per day, is associated with improved adherence. This study examined the potential patient and clinical factors that influence clinicians to convert pediatric patients from immediate-release to ER-Tac. This prospective multi-center observational study followed Canadian pediatric kidney transplant recipients up to 5 years post-transplant. Cox Proportional Hazards Regression was used to examine the influence of factors on conversion to ER-Tac. Sixty-six participants were included in this analysis. For every additional year of age at the time of transplant, the likelihood of conversion was more than doubled (HR 2.54, CI 1.83, 3.54, P < 0.001). The impact of age reduced by three percent for every month after transplant (HR 0.97, CI 0.95, 0.98, P < 0.001). Girls were more likely to be converted than boys (HR 3.78, CI 1.35, 10.6, P 0.01). Adherence measures (MAM-MM and tacrolimus trough variability), individual barriers to adherence, renal function, HLA mismatch, and rejection were not significant predictors of conversion in the final regression model. ER-Tac was preferentially prescribed to older age and female patients. Female sex and adolescence are both associated with worse graft outcomes, but we found no link between individualized markers of adherence/graft risk and conversion. Clinicians appeared to be using demographic features to distinguish patients at perceived higher risk and converted accordingly, without a case-by-case evaluation of who is more susceptible to poor outcomes.
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http://dx.doi.org/10.1111/petr.13959DOI Listing
December 2020

Phospholipase A2 group XV activity during cardiopulmonary bypass surgery.

Clin Biochem 2021 Feb 9;88:49-55. Epub 2020 Dec 9.

Manitoba Centre for Proteomics & Systems Biology, University of Manitoba & Health Sciences Centre, Manitoba, Canada; Department of Internal Medicine, Section of Nephrology, University of Manitoba, Manitoba, Canada; Department of Internal Medicine, Section of Biomedical Proteomics, University of Manitoba, Manitoba, Canada; Department of Immunology, University of Manitoba, Manitoba, Canada.

Objectives: All patients who undergo cardiopulmonary bypass (CPB) experience some degree of ischemia reperfusion injury (IRI). Severe IRI-induced acute kidney injury (AKI) occurs in approximately 1-2% of patients undergoing CPB. Previous studies using activity-based protein profiling of urine identified group XV phospholipase A2, PLA2G15/LPLA2, as potentially associated with patients who develop AKI post CPB. The present study examined urinary PLA2G15/LPLA2 activity during CPB and in the near postoperative period for associations with subsequent AKI development.

Design & Methods: Samples were collected in a nested case controlled cohort of 21 patients per group who either did (AKI) or did not (non-AKI) develop AKI post-operatively. Serum and urine samples from each patient before, during and after CPB were assayed for PLA2G15/LPLA2 activity.

Results: Urine activity significantly increased during the intra operative period. In contrast the activities in paired sera were markedly decreased during CPB. There was no correlation between the serum and urine activity levels of patients. There were no significant differences in activity levels of PLA2G15/LPLA2 in the urine or sera from patients that did and did not develop AKI.

Conclusions: The lack of correlation between serum and urine activity levels suggests that the rapid intraoperative increases in PLA2G15/LPLA2 activity may originate from the kidney and as such offer an intraoperative indicator of early renal response to CPB associated stressors.
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http://dx.doi.org/10.1016/j.clinbiochem.2020.12.003DOI Listing
February 2021

Defining the structural basis for human leukocyte antigen reactivity in clinical transplantation.

Sci Rep 2020 10 27;10(1):18397. Epub 2020 Oct 27.

National University Centre for Organ Transplantation (NUCOT), National University Hospital, Singapore, Singapore.

The current state-of-the-art technology employed to assess anti-human leukocyte antigen antibodies (Anti-HLA Ab) for donor-recipient matching and patient risk stratification in renal transplantation is the single antigen bead (SAB) assay. However, there are limitations to the SAB assay as it is not quantitative and due to variations in techniques and reagents, there is no standardization across laboratories. In this study, a structurally-defined human monoclonal alloantibody was employed to provide a mechanistic explanation for how fundamental alloantibody biology influences the readout from the SAB assay. Performance of the clinical SAB assay was evaluated by altering Anti-HLA Ab concentration, subclass, and detection reagents. Tests were conducted in parallel by two internationally accredited laboratories using standardized protocols and reagents. We show that alloantibody concentration, subclass, laboratory-specific detection devices, subclass-specific detection reagents all contribute to a significant degree of variation in the readout. We report a significant prozone effect affecting HLA alleles that are bound strongly by the test alloantibody as opposed to those bound weakly and this phenomenon is independent of complement. These data highlight the importance for establishing international standards for SAB assay calibration and have significant implications for our understanding of discordance in previous studies that have analyzed its clinical relevance.
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http://dx.doi.org/10.1038/s41598-020-75355-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7591533PMC
October 2020

Validity and utility of urinary CXCL10/Cr immune monitoring in pediatric kidney transplant recipients.

Am J Transplant 2020 Oct 8. Epub 2020 Oct 8.

Nephrology, University of Manitoba, Winnipeg, Manitoba, Canada.

Individualized posttransplant immunosuppression is hampered by suboptimal monitoring strategies. To validate the utility of urinary CXCL10/Cr immune monitoring in children, we conducted a multicenter prospective observational study in children <21 years with serial and biopsy-associated urine samples (n = 97). Biopsies (n = 240) were categorized as normal (NOR), rejection (>i1t1; REJ), indeterminate (IND), BKV infection, and leukocyturia (LEU). An independent pediatric cohort of 180 urines was used for external validation. Ninety-seven patients aged 11.4 ± 5.5 years showed elevated urinary CXCL10/Cr in REJ (3.1, IQR 1.1, 16.4; P < .001) and BKV nephropathy (median = 5.6, IQR 1.3, 26.9; P < .001) vs. NOR (0.8, IQR 0.4, 1.5). The AUC for REJ vs. NOR was 0.76 (95% CI 0.66-0.86). Low (0.63) and high (4.08) CXCL10/Cr levels defined high sensitivity and specificity thresholds, respectively; validated against an independent sample set (AUC = 0.76, 95% CI 0.66-0.86). Serial urines anticipated REJ up to 4 weeks prior to biopsy and declined within 1 month following treatment. Elevated mean CXCL10/Cr was correlated with first-year eGFR decline (ρ = -0.37, P ≤ .001), particularly when persistently exceeding ≥4.08 (ratio = 0.81; P < .04). Useful thresholds for urinary CXCL10/Cr levels reproducibly define the risk of rejection, immune quiescence, and decline in allograft function for use in real-time clinical monitoring in children.
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http://dx.doi.org/10.1111/ajt.16336DOI Listing
October 2020

Early surveillance biopsy utilization and management of pediatric renal allograft acute T cell-mediated rejection in Canadian centers: Observations from the PROBE multicenter cohort study.

Pediatr Transplant 2021 Mar 7;25(2):e13870. Epub 2020 Oct 7.

Department of Pediatrics, University of British Columbia, Vancouver, BC, Canada.

Background: Early TCMR surveillance with protocol kidney biopsy is used differentially among pediatric kidney transplant centers. Little has been reported about actual center-based differences, and this variability may influence TCMR ascertainment, treatment, and monitoring more broadly.

Methods: Data from the PROBE multicenter study were used to identify patients from centers conducting ESB or LSIB. ESB was defined as >50% of patients having at least 1 surveillance biopsy in the first 9 months. Patients were compared for number of biopsies, rejection episodes, treatment, and follow-up monitoring.

Results: A total of 261 biopsies were performed on 97 patients over 1-2 years of follow-up. A total of 228 (87%) of biopsies were performed in ESB centers. Compared to LSIB centers, ESB centers had 7-fold more episodes of TCMR diagnosed on any biopsy [0.8 ± 1.2 vs 0.1 ± 0.4; P < .001] and a 3-fold higher rate from indication biopsies [0.3 ± 0.9 vs 0.1 ± 0.3; P = .04]. The proportion of rejection treatment varied based on severity: Banff borderline i1t1 (40%);>i1t1 and < Banff 1A (86%); and ≥ Banff 1A (100%). Biopsies for follow-up were performed after treatment in 80% of cases (n = 28) of rejection almost exclusively at ESB centers, with 17 (61%) showing persistence of TCMR (≥i1t1).

Conclusions: Practice variation exists across Canadian pediatric renal transplant centers with ESB centers identifying more episodes of rejection. Additionally, treatment of Banff borderline is not universal and varies with severity regardless of center type. Lastly, follow-up biopsies are performed inconsistently and invariably show persistence of rejection.
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http://dx.doi.org/10.1111/petr.13870DOI Listing
March 2021

A noninferiority design for a delayed calcineurin inhibitor substitution trial in kidney transplantation.

Am J Transplant 2020 Sep 21. Epub 2020 Sep 21.

Translational Transplant Research Center, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York.

Improving long-term kidney transplant outcomes requires novel treatment strategies, including delayed calcineurin inhibitor (CNI) substitution, tested using informative trial designs. An alternative approach to the usual superiority-based trial is a noninferiority trial design that tests whether an investigational agent is not unacceptably worse than standard of care. An informative noninferiority design, with biopsy-proven acute rejection (BPAR) as the endpoint, requires determination of a prespecified, evidence-based noninferiority margin for BPAR. No such information is available for delayed CNI substitution in kidney transplantation. Herein we analyzed data from recent kidney transplant trials of CNI withdrawal and "real world" CNI- based standard of care, containing subjects with well-documented evidence of immune quiescence at 6 months posttransplant-ideal candidates for delayed CNI substitution. Our analysis indicates an evidence-based noninferiority margin of 13.8% for the United States Food and Drug Administration's composite definition of BPAR between 6 and 24 months posttransplant. Sample size estimation determined that ~225 randomized subjects would be required to evaluate noninferiority for this primary clinical efficacy endpoint, and superiority for a renal function safety endpoint. Our findings provide the basis for future delayed CNI substitution noninferiority trials, thereby increasing the likelihood they will provide clinically implementable results and achieve regulatory approval.
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http://dx.doi.org/10.1111/ajt.16311DOI Listing
September 2020

More precise donor-recipient matching: the role of eplet matching.

Curr Opin Nephrol Hypertens 2020 Nov;29(6):630-635

Department of Medicine, University of Manitoba.

Purpose Of Review: A precise understanding of the alloimmune risk faced by individual recipients at the time of transplant is an unmet need in transplantation. Although conventional HLA donor-recipient mismatch is too imprecise to fulfil this need, HLA molecular mismatch increases the precision in alloimmune risk assessment by quantifying the difference between donors and recipients at the molecular level.

Recent Findings: Within each conventional HLA mismatch the number, type, and position of mismatched amino acids create a wide range of HLA molecular mismatches between recipients and donors. Multiple different solid organ transplant groups from across the world have correlated HLA molecular mismatch with transplant outcomes including de novo donor-specific antibody development, antibody-mediated rejection, T-cell-mediated rejection, and allograft survival.

Summary: All alloimmunity is driven by differences between donors and recipients at the molecular level. HLA molecular mismatch may represent an advancement compared to traditional HLA antigen mismatch as a fast, reproducible, cost-effective way to improve alloimmune risk assessment at the time of transplantation to move the field towards precision medicine.
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http://dx.doi.org/10.1097/MNH.0000000000000649DOI Listing
November 2020

Adequate tacrolimus exposure modulates the impact of HLA class II molecular mismatch: a validation study in an American cohort.

Am J Transplant 2021 01 11;21(1):322-328. Epub 2020 Oct 11.

Department of Medicine, University of Colorado, Aurora, Colorado, USA.

Clinicians have few tools to predict the risk of alloimmune injury that would guide immunosuppression management in renal transplant patients. We evaluated human leukocyte antigen (HLA)-DR/DQ molecular mismatch to predict de novo donor-specific antibodies (DSAs) during the first year of transplant and explored how differences in tacrolimus exposure may modulate this risk. HLA-DR and -DQ eplet mismatches were determined between 444 donor-recipient pairs in Denver, Colorado between 2007 and 2013. Previously defined mismatch thresholds stratified recipients into low- (N = 119), intermediate- (N = 153), and high- (N = 172) risk categories. The area under the curve for DSA at 1 year was 0.84 and 0.82 for HLA-DR and HLA-DQ eplet mismatches, respectively. Compared to low-risk patients, there was a graded increase in risk of DR/DQ DSA in intermediate (HR 15.39, 95% CI 2.01-118.09, p = .009) and high-risk (HR 23.81, 95% CI 3.17-178.66, p = 0.002) categories. Intermediate- and high-risk patients with a mean tacrolimus <6 ng/ml versus >8 ng/ml had increased risk of DR/DQ DSA at 1 year (HR 2.34, 95% CI 1.05-5.22, p = .04). HLA molecular mismatch represents a reproducible, objective, and clinically relevant tool to stratify patients by alloimmune risk and may help guide personalized immunosuppression management.
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http://dx.doi.org/10.1111/ajt.16290DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7821185PMC
January 2021

Molecular Mismatch-the Renaissance of HLA in Kidney Transplantation.

J Am Soc Nephrol 2020 09 6;31(9):1922-1925. Epub 2020 Aug 6.

Department of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada.

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http://dx.doi.org/10.1681/ASN.2020071011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7461661PMC
September 2020

Activity-based protein profiling guided identification of urine proteinase 3 activity in subclinical rejection after renal transplantation.

Clin Proteomics 2020 16;17:23. Epub 2020 Jun 16.

Manitoba Centre for Proteomics and Systems Biology, 799 John Buhler Research Centre, 715 McDermot Ave., Winnipeg, MB R3E3P4 Canada.

Background: The pathophysiology of subclinical versus clinical rejection remains incompletely understood given their equivalent histological severity but discordant graft function. The goal was to evaluate serine hydrolase enzyme activities to explore if there were any underlying differences in activities during subclinical versus clinical rejection.

Methods: Serine hydrolase activity-based protein profiling (ABPP) was performed on the urines of a case control cohort of patients with biopsy confirmed subclinical or clinical transplant rejection. In-gel analysis and affinity purification with mass spectrometry were used to demonstrate and identify active serine hydrolase activity. An assay for proteinase 3 (PR3/PRTN3) was adapted for the quantitation of activity in urine.

Results: In-gel ABPP profiles suggested increased intensity and diversity of serine hydrolase activities in urine from patients undergoing subclinical versus clinical rejection. Serine hydrolases (n = 30) were identified by mass spectrometry in subclinical and clinical rejection patients with 4 non-overlapping candidates between the two groups (i.e. ABHD14B, LTF, PR3/PRTN3 and PRSS12). Western blot and the use of a specific inhibitor confirmed the presence of active PR3/PRTN3 in samples from patients undergoing subclinical rejection. Analysis of samples from normal donors or from several serial post-transplant urines indicated that although PR3/PRTN3 activity may be highly associated with low-grade subclinical inflammation, the enzyme activity was not restricted to this patient group.

Conclusions: There appear to be limited qualitative and quantitative differences in serine hydrolase activity in patients with subclinical versus clinical renal transplant rejection. The majority of enzymes identified were present in samples from both groups implying that in-gel quantitative differences may largely relate to the activity status of shared enzymes. However qualitative compositional differences were also observed indicating differential activities. The PR3/PRTN3 analyses indicate that the activity status of urine in transplant patients is dynamic possibly reflecting changes in the underlying processes in the transplant. These data suggest that differential serine hydrolase pathways may be active in subclinical versus clinical rejection which requires further exploration in larger patient cohorts. Although this study focused on PR3/PRTN3, this does not preclude the possibility that other enzymes may play critical roles in the rejection process.
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http://dx.doi.org/10.1186/s12014-020-09284-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7296916PMC
June 2020

Patient-centred and family-centred care of critically ill patients who are potential organ donors: a qualitative study protocol of family member perspectives.

BMJ Open 2020 06 15;10(6):e037527. Epub 2020 Jun 15.

Department of Critical Care, Ottawa Hospital, Ottawa, Ontario, Canada

Introduction: In a patient-centred and family-centred approach to organ donation, compassion is paramount. Recent guidelines have called for more research, interventions and approaches aimed at improving and supporting the families of critically ill patients. The objective of this study is to help translate patient-centred and family-centred care into practice in deceased organ donation.

Methods And Analysis: This will be a national, qualitative study of family members of deceased organ donors in Canada. We will include family members who had been approached regarding an organ donation decision, including those who agreed and declined, at least 2 months and no later than 3 years after the patients' death. Data collection and analysis is ongoing and will continue until September 2020 to include approximately 250 participants. Family members will be identified and recruited from provincial organ donation organisation databases. Four experienced qualitative researchers will conduct telephone interviews in English or French with audio-recording for subsequent transcription. The research team will develop a codebook iteratively through this process using inductive methods, thus generating themes directly from the dataset.

Ethics And Dissemination: Local research ethics boards (REB) at all participating sites across Canada have approved this protocol. The main REB involved is the Ottawa Health Science Network REB. Data collection began in August 2018. Publication of results is anticipated in 2021. Study findings will help improve healthcare provider competency in caring for potential organ donors and their families and improve organ donation consent rates. Findings will also help with the development of educational materials for a competency-based curriculum for critical care residents.
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http://dx.doi.org/10.1136/bmjopen-2020-037527DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7299025PMC
June 2020

What have we learned about how to prevent and treat antibody-mediated rejection in kidney transplantation?

Am J Transplant 2020 06;20 Suppl 4:12-22

Department of Internal Medicine, Max Rady College of Medicine, University of Manitoba, Winnipeg, Canada.

Antibody-mediated rejection (ABMR) in kidney transplantation is a major cause of late graft loss, and despite all efforts to date the "standard of care" remains plasmapheresis, IVIg, and steroids, which itself is based on low quality evidence. This review focuses on the risk factors leading to memory and de novo donor-specific antibody (DSA)-associated ABMR, the optimal prevention strategies for ABMR, and advances in  adjunctive and emerging therapies for ABMR. Because new agents require regulatory approval via a Phase 3 randomized control trial (RCT), an overview of progress in innovative trial design for ABMR is provided. Finally, based on the insights gained in the biology of ABMR, current knowledge gaps are identified for future research that could significantly affect our understanding of how to optimally treat ABMR.
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http://dx.doi.org/10.1111/ajt.15859DOI Listing
June 2020

The Fourth International Workshop on Clinical Transplant Tolerance.

Am J Transplant 2021 01 22;21(1):21-31. Epub 2020 Jul 22.

Department of Surgery, Starzl Transplantation Institute, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.

The International Workshop on Clinical Transplant Tolerance is a biennial meeting that aims to provide an update on the progress of studies of immunosuppression minimization or withdrawal in solid organ transplantation. The Fourth International Workshop on Clinical Tolerance was held in Pittsburgh, Pennsylvania, September 5-6, 2019. This report is a summary of presentations on the status of clinical trials designed to minimize or withdraw immunosuppressive drugs in kidney, liver, and lung transplantation without subsequent evidence of rejection. All protocols had in common the use of donor or recipient cell therapy combined with organ transplantation. The workshop also included presentations of mechanistic studies designed to improve understanding of the cellular and molecular basis of tolerance and to identify potential predictors/biomarkers of tolerance. Strategies to enhance the safety of hematopoietic cell transplantation and to improve patient selection/risk stratification for clinical trials were also discussed.
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http://dx.doi.org/10.1111/ajt.16139DOI Listing
January 2021

The Banff 2019 Kidney Meeting Report (I): Updates on and clarification of criteria for T cell- and antibody-mediated rejection.

Am J Transplant 2020 09 28;20(9):2318-2331. Epub 2020 May 28.

Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, Canada.

The XV. Banff conference for allograft pathology was held in conjunction with the annual meeting of the American Society for Histocompatibility and Immunogenetics in Pittsburgh, PA (USA) and focused on refining recent updates to the classification, advances from the Banff working groups, and standardization of molecular diagnostics. This report on kidney transplant pathology details clarifications and refinements to the criteria for chronic active (CA) T cell-mediated rejection (TCMR), borderline, and antibody-mediated rejection (ABMR). The main focus of kidney sessions was on how to address biopsies meeting criteria for CA TCMR plus borderline or acute TCMR. Recent studies on the clinical impact of borderline infiltrates were also presented to clarify whether the threshold for interstitial inflammation in diagnosis of borderline should be i0 or i1. Sessions on ABMR focused on biopsies showing microvascular inflammation in the absence of C4d staining or detectable donor-specific antibodies; the potential value of molecular diagnostics in such cases and recommendations for use of the latter in the setting of solid organ transplantation are presented in the accompanying meeting report. Finally, several speakers discussed the capabilities of artificial intelligence and the potential for use of machine learning algorithms in diagnosis and personalized therapeutics in solid organ transplantation.
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http://dx.doi.org/10.1111/ajt.15898DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7496245PMC
September 2020

PIRs mediate innate myeloid cell memory to nonself MHC molecules.

Science 2020 06 7;368(6495):1122-1127. Epub 2020 May 7.

Thomas E. Starzl Transplantation Institute and Department of Surgery, University of Pittsburgh, Pittsburgh, PA, USA.

Immunological memory specific to previously encountered antigens is a cardinal feature of adaptive lymphoid cells. However, it is unknown whether innate myeloid cells retain memory of prior antigenic stimulation and respond to it more vigorously on subsequent encounters. In this work, we show that murine monocytes and macrophages acquire memory specific to major histocompatibility complex I (MHC-I) antigens, and we identify A-type paired immunoglobulin-like receptors (PIR-As) as the MHC-I receptors necessary for the memory response. We demonstrate that deleting PIR-A in the recipient or blocking PIR-A binding to donor MHC-I molecules blocks memory and attenuates kidney and heart allograft rejection. Thus, innate myeloid cells acquire alloantigen-specific memory that can be targeted to improve transplant outcomes.
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http://dx.doi.org/10.1126/science.aax4040DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7379379PMC
June 2020

Sensitization in transplantation: Assessment of risk (STAR) 2019 Working Group Meeting Report.

Am J Transplant 2020 10 27;20(10):2652-2668. Epub 2020 May 27.

Department of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada.

The purpose of the STAR 2019 Working Group was to build on findings from the initial STAR report to further clarify the expectations, limitations, perceptions, and utility of alloimmune assays that are currently in use or in development for risk assessment in the setting of organ transplantation. The goal was to determine the precision and clinical feasibility/utility of such assays in evaluating both memory and primary alloimmune risks. The process included a critical review of biologically driven, state-of-the-art, clinical diagnostics literature by experts in the field and an open public forum in a face-to-face meeting to promote broader engagement of the American Society of Transplantation and American Society of Histocompatibility and Immunogenetics membership. This report summarizes the literature review and the workshop discussions. Specifically, it highlights (1) available assays to evaluate the attributes of HLA antibodies and their utility both as clinical diagnostics and as research tools to evaluate the effector mechanisms driving rejection; (2) potential assays to assess the presence of alloimmune T and B cell memory; and (3) progress in the development of HLA molecular mismatch computational scores as a potential prognostic biomarker for primary alloimmunity and its application in research trial design.
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http://dx.doi.org/10.1111/ajt.15937DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7586936PMC
October 2020

Evidence for the alloimmune basis and prognostic significance of Borderline T cell-mediated rejection.

Am J Transplant 2020 09 9;20(9):2499-2508. Epub 2020 Apr 9.

Department of Medicine, University of Manitoba, Winnipeg, Canada.

Prognostic biomarkers of T cell-mediated rejection (TCMR) have not been adequately studied in the modern era. We evaluated 803 renal transplant recipients and correlated HLA-DR/DQ molecular mismatch alloimmune risk categories (low, intermediate, high) with the severity, frequency, and persistence of TCMR. Allograft survival was reduced in recipients with Banff Borderline (hazard ratio [HR] 2.4, P = .003) and Banff ≥ IA TCMR (HR 4.3, P < .0001) including a subset who never developed de novo donor-specific antibodies (P = .002). HLA-DR/DQ molecular mismatch alloimmune risk categories were multivariate correlates of Banff Borderline and Banff ≥ IA TCMR and correlated with the severity and frequency of rejection episodes. Recipient age, HLA-DR/DQ molecular mismatch category, and cyclosporin vs tacrolimus immunosuppression were independent correlates of Banff Borderline and Banff ≥ IA TCMR. In the subset treated with tacrolimus (720/803) recipient age, HLA-DR/DQ molecular mismatch category, and tacrolimus coefficient of variation were independent correlates of TCMR. The correlation of HLA-DR/DQ molecular mismatch category with TCMR, including Borderline, provides evidence for their alloimmune basis. HLA-DR/DQ molecular mismatch may represent a precise prognostic biomarker that can be applied to tailor immunosuppression or design clinical trials based on individual patient risk.
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http://dx.doi.org/10.1111/ajt.15860DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7496654PMC
September 2020

Donation after circulatory determination of death in western Canada: a multicentre study of donor characteristics and critical care practices.

Can J Anaesth 2020 05 25;67(5):521-531. Epub 2020 Feb 25.

Southern Alberta Transplant Program, Calgary, AB, Canada.

Purpose: Donation after circulatory determination of death (DCD) has been performed in Canada since 2006. Numerous aspects of donor management remain controversial.

Methods: We performed a multicentre cohort study involving potential DCD donors in western Canada (2008-2017), as well as recipients of their organs, to describe donor characteristics and critical care practices, and their relation to one-year recipient and graft survival.

Results: There were 257 patients in four provinces that underwent withdrawal of life-sustaining therapies (WLST) in anticipation of possible DCD. The proportion of patients that died within two hours of WLST ranged from 67% to 88% across provinces (P = 0.06), and was predicted by deeper coma (P = 0.01), loss of pupillary light or corneal reflexes (P = 0.02), and vasopressor use (P = 0.01). There were significant differences between provinces in time intervals from onset of hypotension to death (9-11 min; P = 0.02) and death to vascular cannulation (7-10 min; P < 0.001). There was inconsistency in pre-mortem heparin administration (82-96%; P = 0.03), including timing (before vs after WLST; P < 0.001) and dose (≥ 300 vs < 300 units·kg; P < 0.001). Donation after circulatory death provided organs for 321 kidney, 81 liver, and 50 lung transplants. One-year recipient and graft survival did not differ among provinces (range 85-90%, P = 0.45). Predictors of death or graft failure included older recipient age (odds ratio [OR] per year, 1.04; 95% confidence interval [CI],1.01 to 1.07) and male donor sex (OR, 3.35; 95% CI, 1.39 to 8.09), but not time intervals between WLST and cannulation or practices related to heparin use.

Conclusion: There is significant variability in critical care DCD practices in western Canada, but this has not resulted in significant differences in recipient or graft survival. Further research is required to guide optimal management of potential DCD donors.
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http://dx.doi.org/10.1007/s12630-020-01594-8DOI Listing
May 2020

Use of biomarkers to improve immunosuppressive drug development and outcomes in renal organ transplantation: A meeting report.

Am J Transplant 2020 06 17;20(6):1495-1502. Epub 2020 Mar 17.

Critical Path Institute, Tucson, Arizona, USA.

On September 27-28, 2018 the Food and Drug Administration (FDA) and the Critical Path Institute's Transplant Therapeutics Consortium convened a public workshop titled "Evidence-Based Treatment Decisions in Transplantation: The Right Dose & Regimen for the Right Patient/Individualized Treatment." The workshop facilitated cooperative engagement of transplant community stakeholders, including pharmaceutical industry, academic researchers, clinicians, patients, and regulators to discuss methods to advance the development of novel immunosuppressive drugs for use in solid organ transplantation. Day 1 focused on the utility of biomarkers in drug development with considerations for seeking regulatory endorsement for use in clinical trials. Biomarkers add value to drug development by improving patient selection criteria, safety monitoring, endpoint selection, and more. Regulatory endorsement through the FDA Biomarker Qualification Program encourages the use of biomarkers in drug development by instilling confidence and consistency in biomarker interpretation across trials. Public-private partnerships or consortia allow stakeholders to share expertise, resources, and data in pursuit of biomarker qualification. Biomarkers relevant to pretransplant risk assessment, early posttransplant care, and assessment of immune response, immunosuppressive drug efficacy, and graft function as discussed on day 1 of the workshop are described.
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http://dx.doi.org/10.1111/ajt.15833DOI Listing
June 2020

Technical Considerations and Confounders for Urine CXCL10 Chemokine Measurement.

Transplant Direct 2020 Jan 24;6(1):e519. Epub 2019 Dec 24.

Transplantation Immunology, Department of Biomedicine, University of Basel, Basel, Switzerland.

Background: The urine C-X-C motif chemokine 10 (CXCL10) is a promising screening biomarker for renal allograft rejection. The aim of the study was to investigate important technical and biological aspects as well as potential confounders when measuring urine CXCL10.

Methods: We analyzed 595 urine samples from 117 patients, who participated in a randomized controlled trial investigating the clinical utility of urine CXCL10 monitoring for posttransplant management. Urine CXCL10 was measured by an immunoassay using electrochemiluminescence.

Results: Intraassay coefficient of variation was 2.5%, and interassay coefficient of variation was 10%. Urine CXCL10 remained stable (ie, <10% degradation) for 8 hours at 25°C or 37°C and for 3 days at 4°C. CXCL10 concentrations [pg/mL] strongly correlated with urine CXCL10/creatinine ratios [ng/mmol] (r = 0.98; < 0.0001). Leucocyturia and active BK-polyomavirus infection are associated with higher CXCL10 concentrations, while allograft function, serum CRP, patient age, proteinuria, urine pH, hematuria, squamous epithelia cell count, and bacteriuria did not correlate with urine CXCL10 concentrations. In 145 paired samples obtained within 1-2 weeks, 80% showed a CXCL10/creatinine ratio change of < ±2 ng/mmol or ±50%, respectively.

Conclusions: Urine CXCL10 measurement on the used platform is accurate and robust. Leucocyturia and active BK-polyomavirus infection are major confounders, which can be easily detected but represent important diagnostic "blind spots" when using urine CXCL10 to screen for allograft rejection. The intraindividual biological variability of urine CXCL10 within 1-2 weeks is mostly below ±50%, which is still much higher than the technical variability due to sample handling/processing (<20%).
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http://dx.doi.org/10.1097/TXD.0000000000000959DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6964934PMC
January 2020

Recommended Treatment for Antibody-mediated Rejection After Kidney Transplantation: The 2019 Expert Consensus From the Transplantion Society Working Group.

Transplantation 2020 05;104(5):911-922

Centre for Transplant and Renal Research, Westmead Institute of Medical Research, University of Sydney and Renal Unit, Westmead Hospital, NSW, Australia.

With the development of modern solid-phase assays to detect anti-HLA antibodies and a more precise histological classification, the diagnosis of antibody-mediated rejection (AMR) has become more common and is a major cause of kidney graft loss. Currently, there are no approved therapies and treatment guidelines are based on low-level evidence. The number of prospective randomized trials for the treatment of AMR is small, and the lack of an accepted common standard for care has been an impediment to the development of new therapies. To help alleviate this, The Transplantation Society convened a meeting of international experts to develop a consensus as to what is appropriate treatment for active and chronic active AMR. The aim was to reach a consensus for standard of care treatment against which new therapies could be evaluated. At the meeting, the underlying biology of AMR, the criteria for diagnosis, the clinical phenotypes, and outcomes were discussed. The evidence for different treatments was reviewed, and a consensus for what is acceptable standard of care for the treatment of active and chronic active AMR was presented. While it was agreed that the aims of treatment are to preserve renal function, reduce histological injury, and reduce the titer of donor-specific antibody, there was no conclusive evidence to support any specific therapy. As a result, the treatment recommendations are largely based on expert opinion. It is acknowledged that properly conducted and powered clinical trials of biologically plausible agents are urgently needed to improve patient outcomes.
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http://dx.doi.org/10.1097/TP.0000000000003095DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7176344PMC
May 2020

Human leukocyte antigen molecular mismatch to risk stratify kidney transplant recipients.

Curr Opin Organ Transplant 2020 02;25(1):8-14

Department of Medicine, University of Manitoba.

Purpose Of Review: Stalled drug development and the lack of improvement in long-term graft survival reflect the unmet need for prognostic and predictive biomarkers in transplantation. Although conventional human leukocyte antigen (HLA) mismatch is too imprecise to fulfill this need, HLA molecular mismatch increases the precision in alloimmune risk assessment by quantifying the difference between donors and recipients at the molecular level.

Recent Findings: Within each conventional HLA mismatch, recipients exhibit a wide range of HLA molecular mismatches with their donors. Quantifying HLA molecular mismatch improves the precision of alloimmune risk assessment for de novo donor-specific antibody development (dnDSA). Alloimmune risk categories developed analyzing dnDSA development were also found to correlate with T-cell-mediated rejection, antibody-mediated rejection, and all cause graft loss in adjusted and unadjusted models.

Summary: All alloimmunity is driven by differences between donors and recipients at the molecular level. HLA molecular mismatch may represent a fast, reproducible, cost-effective, way to improve alloimmune risk assessment at the time of transplantation to move the field towards precision medicine.
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http://dx.doi.org/10.1097/MOT.0000000000000714DOI Listing
February 2020

Hyperacute Antibody-mediated Rejection Associated With Red Blood Cell Antibodies.

Transplant Direct 2019 Aug 25;5(8):e477. Epub 2019 Jul 25.

Section of Nephrology, Department of Internal Medicine, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, MB, Canada.

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http://dx.doi.org/10.1097/TXD.0000000000000925DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6708630PMC
August 2019

Early Antibody-Mediated Kidney Transplant Rejection Associated With Anti-Vimentin Antibodies: A Case Report.

Am J Kidney Dis 2020 01 9;75(1):138-143. Epub 2019 Sep 9.

Section of Nephrology, Department of Internal Medicine, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, Manitoba, Canada; Department of Immunology, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, Manitoba, Canada. Electronic address:

Improving precision in predicting alloreactivity is an important unmet need and may require individualized consideration of non-HLA antibodies. We report a 21-year-old man with kidney failure from immunoglobulin A nephropathy who met all traditional criteria for a "low-risk" transplant for immune memory. He was unsensitized and received a haplotype-matched living donor kidney transplant from his mother. There were no anti-HLA donor-specific antibodies and flow cross-match was negative. After immediate function, he developed delayed graft function on postoperative day 2. The transplant biopsy specimen was suggestive of antibody-mediated rejection and acute tubular injury with increased vimentin proximal tubular expression compared to the implantation biopsy specimen. He had a history of juvenile idiopathic arthritis, and non-HLA antibody screening demonstrated preformed anti-vimentin antibody. He was successfully treated with plasmapheresis, intravenous immunoglobulin, antithymocyte globulin, and methylprednisolone, with renal recovery. The follow-up biopsy specimen demonstrated decreased vimentin expression with decreased alloinflammation, and graft function remains stable at 1 year posttransplantation (estimated glomerular filtration rate, 62mL/min/1.73m). We postulate that preformed anti-vimentin autoantibodies bound to vimentin expressed on apoptotic tubular epithelial cells induced by ischemia-reperfusion injury and to constitutively expressed vimentin on peritubular capillaries and podocytes. Our case is suggestive of the involvement of anti-vimentin antibody, for which the pathogenic epitopes may be exposed during ischemia-reperfusion injury.
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http://dx.doi.org/10.1053/j.ajkd.2019.06.010DOI Listing
January 2020

Activity-based Protein Profiling Approaches for Transplantation.

Transplantation 2019 09;103(9):1790-1798

Manitoba Centre for Proteomics and Systems Biology, Winnipeg, MB, Canada.

Enzyme activity may be more pathophysiologically relevant than enzyme quantity and is regulated by changes in conformational status that are undetectable by traditional proteomic approaches. Further, enzyme activity may provide insights into rapid physiological responses to inflammation/injury that are not dependent on de novo protein transcription. Activity-based protein profiling (ABPP) is a chemical proteomic approach designed to characterize and identify active enzymes within complex biological samples. Activity probes have been developed to interrogate multiple enzyme families with broad applicability, including but not limited to serine hydrolases, cysteine proteases, matrix metalloproteases, nitrilases, caspases, and histone deacetylases. The goal of this overview is to describe the overall rationale, approach, methods, challenges, and potential applications of ABPP to transplantation research. To do so, we present a case example of urine serine hydrolase ABPP in kidney transplant rejection to illustrate the utility and workflow of this analytical approach. Ultimately, developing novel transplant therapeutics is critically dependent on understanding the pathophysiological processes that result in loss of transplant function. ABPP offers a new dimension for characterizing dynamic changes in clinical samples. The capacity to identify and measure relevant enzyme activities provides fresh opportunities for understanding these processes and may help identify markers of disease activity for the development of novel diagnostics and real-time monitoring of patients. Finally, these insights into enzyme activity may also help to identify new transplant therapeutics, such as enzyme-specific inhibitors.
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http://dx.doi.org/10.1097/TP.0000000000002752DOI Listing
September 2019

Multicentre randomised controlled trial protocol of urine CXCL10 monitoring strategy in kidney transplant recipients.

BMJ Open 2019 04 11;9(4):e024908. Epub 2019 Apr 11.

Internal Medicine, University of Manitoba College of Medicine, Winnipeg, Manitoba, Canada.

Introduction: Subclinical inflammation is an important predictor of death-censored graft loss, and its treatment has been shown to improve graft outcomes. Urine CXCL10 outperforms standard post-transplant surveillance in observational studies, by detecting subclinical rejection and early clinical rejection before graft functional decline in kidney transplant recipients.

Methods And Analysis: This is a phase ii/iii multicentre, international randomised controlled parallel group trial to determine if the early treatment of rejection, as detected by urine CXCL10, will improve kidney allograft outcomes. Incident adult kidney transplant patients (n~420) will be enrolled to undergo routine urine CXCL10 monitoring postkidney transplant. Patients at high risk of rejection, defined as confirmed elevated urine CXCL10 level, will be randomised 1:1 stratified by centre (n=250). The intervention arm (n=125) will undergo a study biopsy to check for subclinical rejection and biopsy-proven rejection will be treated per protocol. The control arm (n=125) will undergo routine post-transplant monitoring. The primary outcome at 12 months is a composite of death-censored graft loss, clinical biopsy-proven acute rejection, de novo donor-specific antibody, inflammation in areas of interstitial fibrosis and tubular atrophy (Banff i-IFTA, chronic active T-cell mediated rejection) and subclinical tubulitis on 12-month surveillance biopsy. The secondary outcomes include decline of graft function, microvascular inflammation at 12 months, development of IFTA at 12 months, days from transplantation to clinical biopsy-proven rejection, albuminuria, EuroQol five-dimension five-level instrument, cost-effectiveness analysis of the urine CXCL10 monitoring strategy and the urine CXCL10 kinetics in response to rejection therapy.

Ethics And Dissemination: The study has been approved by the University of Manitoba Health Research Ethics Board (HS20861, B2017:076) and the local research ethics boards of participating centres. Recruitment commenced in March 2018 and results are expected to be published in 2023. De-identified data may be shared with other researchers according to international guidelines (International Committee of Medical Journal Editors [ICJME]).

Trial Registration Number: NCT03206801; Pre-results.
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http://dx.doi.org/10.1136/bmjopen-2018-024908DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6500325PMC
April 2019

Comparison of the effects of standard vs low-dose prolonged-release tacrolimus with or without ACEi/ARB on the histology and function of renal allografts.

Am J Transplant 2019 06 1;19(6):1730-1744. Epub 2019 Feb 1.

Health Sciences Centre, Winnipeg, Manitoba, Canada.

Targeting the renin-angiotensin system and optimizing tacrolimus exposure are both postulated to improve outcomes in renal transplant recipients (RTRs) by preventing interstitial fibrosis/tubular atrophy (IF/TA). In this multicenter, prospective, open-label controlled trial, adult de novo RTRs were randomized in a 2 × 2 design to low- vs standard-dose (LOW vs STD) prolonged-release tacrolimus and to angiotensin-converting enzyme inhibitors/angiotensin II receptor 1 blockers (ACEi/ARBs) vs other antihypertensive therapy (OAHT). There were 2 coprimary endpoints: the prevalence of IF/TA at month 6 and at month 24. IF/TA prevalence was similar for LOW vs STD tacrolimus at month 6 (36.8% vs 39.5%; P = .80) and ACEi/ARBs vs OAHT at month 24 (54.8% vs 58.2%; P = .33). IF/TA progression decreased significantly with LOW vs STD tacrolimus at month 24 (mean [SD] change, +0.42 [1.477] vs +1.10 [1.577]; P = .0039). Across the 4 treatment groups, LOW + ACEi/ARB patients exhibited the lowest mean IF/TA change and, compared with LOW + OAHT patients, experienced significantly delayed time to first T cell-mediated rejection. Renal function was stable from month 1 to month 24 in all treatment groups. No unexpected safety findings were detected. Coupled with LOW tacrolimus dosing, ACEi/ARBs appear to reduce IF/TA progression and delay rejection relative to reduced tacrolimus exposure without renin-angiotensin system blockade. ClinicalTrials.gov identifier: NCT00933231.
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http://dx.doi.org/10.1111/ajt.15225DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6590452PMC
June 2019

HLA-DR/DQ molecular mismatch: A prognostic biomarker for primary alloimmunity.

Am J Transplant 2019 06 15;19(6):1708-1719. Epub 2018 Dec 15.

Department of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada.

Alloimmune risk stratification in renal transplantation has lacked the necessary prognostic biomarkers to personalize recipient care or optimize clinical trials. HLA molecular mismatch improves precision compared to traditional antigen mismatch but has not been studied in detail at the individual molecule level. This study evaluated 664 renal transplant recipients and correlated HLA-DR/DQ single molecule eplet mismatch with serologic, histologic, and clinical outcomes. Compared to traditional HLA-DR/DQ whole antigen mismatch, HLA-DR/DQ single molecule eplet mismatch improved the correlation with de novo donor-specific antibody development (area under the curve 0.54 vs 0.84) and allowed recipients to be stratified into low, intermediate, and high alloimmune risk categories. These risk categories were significantly correlated with primary alloimmune events including Banff ≥1A T cell-mediated rejection (P = .0006), HLA-DR/DQ de novo donor-specific antibody development (P < .0001), antibody-mediated rejection (P < .0001), as well as all-cause graft loss (P = .0012) and each of these correlations persisted in multivariate models. Thus, HLA-DR/DQ single molecule eplet mismatch may represent a precise, reproducible, and widely available prognostic biomarker that can be applied to tailor immunosuppression or design clinical trials based on individual patient risk.
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http://dx.doi.org/10.1111/ajt.15177DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6563434PMC
June 2019

A call to action-The transplant recipient's expectation of precision in transplant medicine.

Am J Transplant 2018 12 13;18(12):2845-2846. Epub 2018 Aug 13.

Department of Internal Medicine, Max Rady College of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada.

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http://dx.doi.org/10.1111/ajt.15027DOI Listing
December 2018